A problem with many pipes for liquids, i.e. pipes for distribution of liquids for human consumption, like water distribution pipes, is the occurrence of so called biofilms on the inside surface of the pipe. Due to bacteria, microbes and other cell growths occurs on the inside surface of the pipes. The same problem also occurs on the inside of sewage pipes reducing the flow in the pipe thus causing problems with stop ups and reduced capacity of the sewage system.
Despite reducing the flow capacity of the pipe, when such growths come loose from the surface of pipes distributing liquids for human consumption, people drinking the liquid might get problems such as diarrhea or the like due to bacteria.
Biofilms play an essential barrier role in conventional water treatment through the entrapment of particulate material as well as through nutrient removal. In distribution systems water practitioners have limited control over many of the processes that take place. Within these environments, distribution pipe biofilms can impact on the aesthetic (colour, taste and odour) quality of water and act as a reservoir of opportunistic microbial pathogens such as legionellae, mycobacteria, pseudomonads, campylobacter, enterohaemorrhagic E. coli, helicobacter and salmonella as well as model enteric virions have been shown to accumulate and persist in model systems, and may therefore present an additional source of concern.
Conventionally, disinfectants and microbials like chlorine has been used to reduce the growths of biofilms in pipes distributing liquids for human consumption, like water or other beverage. One of the disadvantages with chlorine is the formation of potentially hazardous disinfection by-products formed through the reaction of natural organic material with chlorine. Further, chlorine changes the taste and smell of the liquid.
In smaller systems for distributing beverage like milk or beer, often the whole system has to be separately cleaned with settled intervals to ensure proper quality of the beverage distributed. Such cleaning is not only costly and time consuming; it is also a risk that rests of cleaning chemicals remain in the system after cleaning, which could lead not only to bad taste of the beverage but also to a risk that unhealthy chemicals are consumed.
Similar problems with growth of biofilms also occurs in tubes for medical uses, like catheters for distributing liquid medicaments.
Attempts to avoid chemicals like chlorine and the like, and instead use electro-assisted methods have been done. In such known equipments, a coil is wound around a partial section of the pipe or duct to remove microbial biofilms. An electric signal is sent to the coil, thereby producing an electromagnetic field in the pipe. Although some effect might be seen, practical tests show that the effect of reducing growths of the biofilms, or removing the biofilms is poor. Further, such a solution with a wounded coil only produces an electromagnetic field in the immediate vicinity of the coil and is thus not applicable to pipes or ducts with a significant length.